.. _CSTR_injection:

Continuously Stirred Tank Reactor with Injection
================================================

.. index::
   pair: watertap.unit_models.cstr_injection;cstr_injection

This CSTR with injection unit model is based on the `IDAES CSTR <https://idaes-pse.readthedocs.io/en/latest/reference_guides/model_libraries/generic/unit_models/cstr.html>`_
with the addition of mass transfer terms. The model makes the following assumptions:

   * is 0-dimensional
   * supports a single liquid phase only
   * supports steady-state only

Degrees of Freedom
------------------
Aside from the inlet feed state variables (i.e. temperature, pressure, component flowrates), the CSTR with injection model has
two degree of freedoms, and additional degrees of freedom may need to be specified depending on the configuration options.

    * volume OR hydraulic retention time
    * injection rates for all components

If heat transfer is included:
    * heat duty

If pressure change is included:
    * change in pressure (ΔP)

If aeration is included, the following degrees of freedom could replace the oxygen injection rate:
    * lumped mass transfer coefficient for oxygen (KLa)
    * dissolved oxygen concentration at equilibrium (:math:`S_{O, eq}`)


Model Structure
---------------
The CSTR with injection unit model consists of a single ControlVolume0D (named control_volume) with one inlet port (named inlet) and one outlet port (named outlet).

Sets
----
.. csv-table::
   :header: "Description", "Symbol", "Indices"

   "Time", ":math:`t`", "[0]"
   "Inlet/outlet", ":math:`x`", "['in', 'out']"
   "Phases", ":math:`p`", "['Liq']"
   "Components", ":math:`j`", "['H2O', 'NaCl']*"

\*Solute depends on the imported property model; example shown here is for the NaCl property model.

Variables
---------
.. csv-table::
   :header: "Description", "Symbol", "Variable Name", "Index", "Units"

   "Hydraulic retention time", ":math:`HRT`", "hydraulic_retention_time", "[t]", ":math:`\text{s}`"
   "Dissolved oxygen concentration at equilibrium", ":math:`S_{O, eq}`", "S_O_eq", "None", ":math:`\text{kg/}\text{m}^3`"
   "Component injection", ":math:`I`", "injection", "[t, p, j]", ":math:`\text{kg/hr}`"
   "Electricity intensity", ":math:`E_{I}`", "energy_electric_flow_vol_inlet", "None", ":math:`\text{kWh/}\text{m}^3`"

Equations and Relationships
---------------------------

.. csv-table::
   :header: "Description", "Equation"

   "CSTR retention time", ":math:`HRT = V / Q_{in}`"
   "Oxygen mass transfer", ":math:`I_{O} = KLa * V * (S_{O, eq} - C_{O})`"
   "Electricity consumption (without aeration)", ":math:`E = E_{I} * Q_{in}`"
   "Electricity consumption (with aeration)", ":math:`E = \frac{S_{O, eq}}{1.8} * V * KLa`"

Class Documentation
-------------------
.. currentmodule:: watertap.unit_models.cstr_injection

.. autoclass:: CSTR_Injection
    :members:
    :noindex: